"It honestly is my one reason for being healthy," Winokur told PEOPLE at the American Diabetes Association's Tour de Cure bike ride in Santa Monica on Thursday. "I never ever did this before, and I truly did it to be there for my son."
"I'm a 40-year-old and I have a 5-year-old kid," she says. "I don't want to be unhealthy. I want to be around for as long as I can."
Now that she's lost the weight, Winokur says her biggest challenge is mental rather than physical.
"I spent last year getting healthy and strong, and taking off the weight, and getting to where I think is a healthy place to live," says the actress. "This next year I have to spend getting my brain up to speed with my weight. It's like my body has changed but my mind hasn't."
"Food is easy," explains Winokur. "I don't crave the crap anymore. I just have to stop saying to myself, 'Ugh you look so fat.' Honestly I say it to myself more now than I did when I was heavier."
Despite the mental hurdles, the star is enjoying her new healthy lifestyle and cites running and hiking as her go-to exercises.
"I can get on a treadmill and run. I watch TV, listen to music and read a magazine all while I'm running!"
When it gets difficult for her to remain committed to staying healthy, Winokur just remembers a conversation she had with her son.
"The other day he's like, 'Mommy you want to live to be 110!' I almost burst out crying."